MAGNETIC-FIELD EFFECTS - MARY, MIMS AND MODS

The principles and methodology of magnetic field effects (MFE) on the yield of photosynthetic reactions are briefly reviewed. Two basically different mechanisms are described: the MFE driven by photochemical ra dical pair production and subsequent spin-selective recombination (Rad ical Pair Mechanism, RPM), and the MFE produced by the magnetic-field induced mixing of the three sublevels of a molecular triplet state (Ma gnetic field Induced Mixing of Sublevels, MIMS). A number of experimen tal methods for measuring so-called MARY (MAgnetic field effect on the Reaction Yield) curves are described. It is shown that the MFE is a p owerful tool for measuring highly accurate Triplet-minus-Singlet absor bance difference spectra (Magneto-Optical Difference Spectroscopy, MOD S). A number of recent applications of the MFE in the study of photosy nthetic reactions is discussed, comprising also an investigation of Op tically-Detected Magnetic Resonance (ODMR) in low magnetic field, whic h suggests that st significant spin-orbit coupling in the triplet stat e of the primary electron donor leads to level anti-crossing.